Define AM33XX control register, in order to allow access to
control register address space, also add CONTROL_SEC_CLK_CTRL
register offset; both are required in clock tree data,
for wdt0 and timer0 clock source select configuration.

CONTROL.SEC_CLK_CTRL register is provided to select/configure
clock input for WDT0 and TIMER0.
Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
[paul@pwsan.com: added include of plat/am33xx.h to fix build break;
 added AM33XX_CONTROL_STATUS bitfields that will be needed for the clock
 tree; fixed some control.h whitespace problems while here]
Signed-off-by: Paul Walmsley <paul@pwsan.com>